Chromate Free Corrosion Resistant Coatings using Water-Dispersible Tannisulfonic Acid-Doped Conducting Polymers and Nanocomposites (TSE03-B)

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Continuing restrictions on volatile organic compounds (VOCs) and heavy metals such as chromium in conversion coatings have made it necessary to search for novel alternatives. Although inherently conducting polymers (ICPs) have long been known to inhibit the corrosion process of metals, their use in industry (with the exception of Ormecon in Europe) has been limited by their insolubility. The ICPs proposed in this project will utilize tanninsulfonic acid, a renewable resource material, as a template/dopant to yield water-dispersible systems. Due to the already known ability of tannin to prevent corrosion, tanninsulfonic acid-doped ICPs should provide environmentally friendly corrosion inhibitors. Since tannins are known to complex metal ions efficiently due to the presence of the o-catechol groups and the fact that certain metal oxo nanocomposites themselves have been shown to inhibit corrosion, metal oxo nanocomposites chelated to tanninsulfonic acid will be synthesized. These tannin based nanocomposites will be used as templates/dopants for the synthesis of novel water-dispersible ICPs. As a result of the synergistic effects, these corrosion inhibitors may prove to be highly effective. The synthesized ICPs will be characterized using various spectroscopic and electrochemical methods. Those that show sufficient conductivity, electroactivity, and dispersibility will be blended with a variety of water-based commercial resins and applied on a variety of substrates including alloys of iron and aluminum that are commonly used in industry. Substrate preparation and coating application will be performed according to ASTM standards. Corrosion testing will be performed using electrochemical corrosion techniques such as electrochemical impedance spectroscopy, cyclic polarization and Tafel plots. The results from these tests will be directly compared with conventional barrier and conversion coatings including chromates. Broader ImpactDue to the high volume of ICPs that could be used in the coating industry, the future of conducting polymers may well lie in their success in corrosion inhibition. In addition, the data generated during this research will be helpful in elucidating the mechanism of corrosion prevention which still remains somewhat elusive. The concept of using a renewable resource as a substitute for a toxic heavy metal as well as in reducing VOCs without sacrificing desirable properties in corrosion resistant coatings is both environmentally and economically appealing and fits well with the scope of this NSF/EPA project. The involvement of students in this project provides them an opportunity to be involved in cutting edge research of importance to the environment that includes elimination of chromates and VOCs at the source, while training them to be polymer chemists. ICPs have already shown promise in the biomedical field especially in the area of nerve regeneration and artificial muscles. A concerted effort will be made to include members of the research community at the nearby medical school in workshops and seminars so that future collaborative projects with our group may be possible.